The present invention relates to the dewatering of peat. The global reserves of peat represent very large quantities of energy. Peat is furthermore a fuel which is environmentally acceptable due to its low sulphur content and low content of ash. In spite of this, peat has not become a major source of fuel except during periods of crises and blockade. This is due to the fact that peat always contains large quantities of water. Solving the dewatering problem has therefore always received much effort in countries with large peat reserves. If it would be possible to economically dewater peat in a mechanical way, peat could be made available for energy production at very low cost and at a very small environmental impact.
The present invention involves a new method to dewater peat mechanically which seems to meet all that could be desired in this connection. The method not only permits economical mechanical dewatering with all the advantages connected with such expedient but also imparts to the peat a suitable consistency for further treatment in the processes of pyrolysis, gasification and hydrogenation.
Many different methods have been proposed for mechanical dewatering of peat. A summary of these methods is presented e.g., in a book "Torv i Sverige" (Peat in Sweden), Stockholm 1977. The prior inventors have tried numerous dewatering techniques, such as chemical methods involving the addition of coagulating electrolytes, as well as thermal methods for more radical changing of the peat structure, so-called wet carbonization, "Vatkolning a torv" (Wet carbonization of peat) 1960, AB Svensk Torvforadling. Several of these methods have been successful from a technical point of view, e.g., the method of wet carbonization mentioned above, but has still not come into general use due to high cost and environmental problems associated with the discharges of waste water from the process.
Evidently, the final step in a process for mechanical dewatering of peat should comprise a pressing step. The various methods have therefore been concerned with the task of conditioning the peat so as to facilitate the pressing operation and render it economical.